Pitch curve

[Eric Hartley]

Hi

At present I'm learning on a Trex450 dfc and have tried various pitch curve settings some ok others definitely not. I watched an U tube video which suggested starting with 0% pitch with stick in low position,6% at mid stick and 10% at full stick. Whilst able to achieve the first two settings on my Tx.the max will only reach 8%. Do I need to alter the end point to get the 10% setting? Incidentally I'm using a Futaba 14sg Tx.

[Allan Bennett]

My first comment would be that you definitely need some negative pitch at the bottom end. The reason is that you'll sometimes need to counter uplift when there's a gust of wind, and it's also better to "plant" it firmly on the ground when you land. I usually go for -3 degrees.

As for maximum pitch, what's stopping you going beyond 10 degrees (I presume % means degrees in your text)? Is it something mechanical (servo throw, swash throw), or the flybarless controller? And which controller is it -- Align's 3Gx or something else?

It may be simply that you have to adjust the lengths of your pushrods (equally) slightly to get the swash operating a little higher up the shaft.

[Chris Barlow]

Yes first adjust your end points to 100% both ways then set zero throttle (bottom of the pitch curve) to at least -10 to -12 degrees pitch. Then see if you can get +10 to +12 degrees pitch at full throttle.

If you can't get it you may need to move the push rod further out on the servo arm to get more movement. Once you get the full range of mechanical movement you need use the end point settings to get about -3 to -5 degrees pitch at zero throttle, +10 to +12 degrees at full throttle at 0 degrees at half throttle and set this to "Idle 0" This should produce a pitch curve starting shallow then getting steeper after half throttle.

For "idle 1" (or sometimes called "Idle up" ) you can adjust the end points to get form -12 to +12 in a straight line going through 0 degrees at half throttle but if you're still learning you won't need this for a while.

On my helis I usually set Idle 0 to -3 degrees for the full range with zero throttle as a safety measure, then Idle 1 from -5 to +12 for "scale" flying with gentle positive g aeros and Idle 2 from -12 to +12 for loops with an inverted hold at the top (not very often! )

[Eric Hartley]

Hi

The model is Trex450 plus dfc with Align 3GXmrs controller which only has two adjustment screws - gain and roll rate neither of which I have touched as they are set at factory settings for beginner (quarter too). I've tried to set it up for hovering only and have not bothered at this stage with idle up 1 & 2. The present pitch curve settings on my Tx. are -30,-10,+10,+50,+80 with a throttle curve of 0,30,55,70,85. Its not bad but I feel I could improve the curves.Incidentally the minus figs. on the pitch curve are because the Futaba 14sg goes from -100 to +100.

[Chris Barlow]

The - and + values for the pitch will relate to the angle of attack of the blades in degrees. Do you have a pitch gauge to measure the pitch you're getting through the throttle stick range?

It's only the angle of the blades that's important which is set up with the linkages from the servos.  The numbers on the radio are just a percentage of the travel of the servos.

Edited By Chris Barlow 1 on 21/09/2014 14:06:58

[Jamie sawyer]

As Chris says, pitch gage is a 100% must Eric....

There is a lot to consider while setting up the helicopter servos before you even go into your pitch curves to get a linear movement in the servo arms versus the swash plate.

With the helicopter sitting on the table you have your motor cables disconnected so the main blades and motor doesn't spool up. Set your throttle pitch curve to 0 - 25 - 50 - 75 - 100.........Throttle curve the same....0 - 25 - 50 - 75 - 100.

Have your transmitter set to normal mode...not idle up mode.

Put your throttle to 50% half way setting!

Check that the 3 servo arms on the swash are at a perfect horizontal position on all 3 servos. Also as you move your throttle up and down make sure all 3 servos are moving in the same direction up and down together. While you have your throttle set to half way on your transmitter and servo arms at a horizontal stage you have to make sure the swash is perfectly level and adjust the servo arm linkages to adjust. Then the pitch gauge comes in and you need it i'm afraid.....set the swash to 4 deg at half throttle.....this is your hovering state to start a good foundation on.

If you get this bit right then the rest follows very easily. You should archive + 12 deg or so at 100% throttle stick. 0% on throttle you require -4 deg on the rotor blades. You can adjust this by your end points in the transmitter.

Idle up 1 can be set now for a more agile flight pattern. You have to unsure that when you click into idle up from the normal setting that there isn't a big difference on the throttle setting or it will affect your helicopter and it will take a jump in the air which is quite off putting. Normally my Idle up settings for my trex are 100% - 80% - 55% - 80% - 100% ON Throttle and my pitch setting is -12 deg at bottom stick 0% deg pitch mid stick and +12 deg top stick.....pitch curve is 0% - 25% - 50% - 75% - 100% but adjust the end point so that you achive the full movement of the swash for you full negative -12 deg....

You have to make sure that you have the beginning setup correct of you will be having an up hill battle all the way.Hope all this makes sense and helps

Jamie

[Chris Barlow]

If this heli is new to you it would be worth setting up completely from scratch anyway. You don't know how it's been set/sdjusted at the factory or by the previous owner and it is a good idea to check that all screws have been threadlocked! Sometimes this is even missing on some screws on brand new helis with expensive and frustrating first flights!

Pitch gauge, steel rule, ball pliers, threadlock and swash plate leveller are a must as well as patience and accuracy!

[Jamie sawyer]

Posted by Chris Barlow 1 on 21/09/2014 15:02:11:

If this heli is new to you it would be worth setting up completely from scratch anyway. You don't know how it's been set/sdjusted at the factory or by the previous owner and it is a good idea to check that all screws have been threadlocked! Sometimes this is even missing on some screws on brand new helis with expensive and frustrating first flights!

Pitch gauge, steel rule, ball pliers, threadlock and swash plate leveller are a must as well as patience and accuracy!

I always eyeball the swash for level Chris, its worked for me for years. If I was aiming for serious accurate 3D flight I would be tempted to buy one but as I say eyeball level is good enough or if you sit the heli on a table like i said and hold a scaffolder's short level along the line of the swash it will give you a good enough eyeball setup.

[Eric Hartley]

Hi

What I have noticed is that there is relatively little movement in the servos with the exception of rudder which seems to move fully left and right. I was wondering whether perhaps the control unit (3gxmrs) is toned down for beginners! even so I would ascertain that the servos ,with the exception of rudder are only moving roughly half distance - maybe worthwhile trying a different controller (was thinking of the Futaba)?

[Jamie sawyer]

Have you watched this Eric....

https://www.youtube.com/watch?v=aiBV1GGRJe8

It sounds like you have a programming issue. It will be something simple but I'm not up to speed on that TX personally. I use Futaba but its the 7ch Fasst set...

I would try resetting the whole model program or just setup a new program for that particular helicopter and see how you get on.